Page 10 of 27 MCM-Inst-1.10
monitors multiple branch circuits or loads on a single service. Note: when describing service types, the
number of wires only includes neutral and line conductors, not the ground conductor.
The MCM only has one set of line voltage connections, so all submeter blocks (SMBs) share the same
line voltages. However, one MCM can monitor different types of loads powered by the same service.
For example, if your MCM line voltage connection is 120/208 wye, the MCM could simultaneously
monitor three-phase wye loads, three-phase delta loads (no neutral), two-wire line-to-line loads (e.g.,
L1 to L2), and single-phase line-to-neutral loads.
Internally, each SMB acts as three separate single-phase meters, one tied to each CT input. By
default, the meter associates CT1 with VoltA
(or V
A
- V
N
), CT2 with VoltB, and CT3 with VoltC. This
default configuration may be changed using the
MeterConfig
registers. When this guide refers to the
MeterConfig
registers, there are three registers,
MeterConfig1
,
MeterConfig2
, and
MeterConfig3
,
associated with
CT1
,
CT2
, and
CT3
respectively.
Connect the line voltages to the MCM inputs, as shown in the following sections. If you are monitoring
different types of loads, be sure to use the line voltage connection for the type of load with the most
wires connected.
3.2.1 Three-Phase, Four-Wire Wye
This is a common commercial and industrial service that includes a neutral conductor. Load #1
is three-phase and could be wye or delta connected. Loads #2, #3, and #4 are single-phase,
line-to-neutral.
V
B
V
C
V
N
V
A
CT2
ADDR+1
ADDR+0
CT1
CT3
CT2 CT1
CT3
Additional Loads
Earth
L3 L2 L1 N
Meter Power
Load #1,
3Ø
Load #2, 1Ø
Load #3, 1Ø
Load #4, 1Ø
Figure 3: Three-Phase Four-Wire Wye
This service supports the following types of loads:
●
Three-phase, four-wire, wye (with neutral):
This requires three CTs. You do not need to change
the
MeterConfig
registers if you wire the CTs as shown for load #1 above, with
CT1
placed
around L1, CT2 around L2, and
CT3
around L3.
●
Three-phase, three-wire, delta (no neutral)
3.2.2 Three-Phase, Three-Wire Delta
below
for details.
●
Single-phase, line-to-neutral:
This is metered with a single CT, as illustrated for loads #2, #3,
and #4. The
MeterConfig
registers may need to be changed.
